Photoresist film covering a surface of a substrate becomes unnecessary after effecting a photoetching treatment in the semi-conductor manufacturing industry. Processes are well known, in which, for instance
(i) the covering film is oxidized by a heated mixture liquid of bichromate and sulfuric acid, or PA1 (ii) the covering film is heated to a high temperature under an oxygen gas current atmosphere in order to be burned, or PA1 (iii) the covering film is peeled off after the same is swelled by being immersed in a high temperature peeling agent, or PA1 (iv) the covering film is oxidized by heating caused by a glow discharge of high frequency under a low pressure oxygen gas current atmosphere.
These known processes, however, are inconvenient in that they result in the contamination of the surface of the substrate, or in the adhesion of impurities thereto, or in damage or deterioration thereof by the oxidizing liquid or the peeling agent, or by the heating, oxidation, burning and charring of the photoresist film. Thus manufacturing losses resulting from defective products cannot be avoided.